Preparation method of amino acid foliar fertilizer extracted based on animal hair

Abstract

The invention relates to the technical field of agricultural fertilizers, and discloses a preparation method of an amino acid foliar fertilizer extracted based on animal hair, and the preparation method comprises the following steps: raw material pretreatment: carrying out plasma modification on animal hair to improve the keratin hydrolysis performance; a double hydrolysis process: firstly decomposing a keratin structure in the hair through sulfuric acid hydrolysis, and then generating free amino acid through enzyme hydrolysis; recycling by-products: preparing biochar or protein feed from undissolved residues generated in the hydrolysis process, and separating and recycling amino acids and salts in waste liquid; and preparing a foliar fertilizer formula: chelating the extracted amino acid concentrated solution with trace elements. The technical effects of zero emission and high-valued conversion of wastes are achieved through a resource utilization scheme that biochar is prepared from undissolved residues through a pyrolysis process or protein feed is prepared from the undissolved residues through secondary enzymolysis, and free amino acids and salts in waste liquid are separated and recycled through a membrane separation and crystallization extraction technology.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural fertilizers, in particular to a method for preparing an amino acid foliar fertilizer based on animal hair extraction. Background Art

[0002] Animal hair is a common industrial waste, which comes from slaughterhouses, tanneries and the textile industry. Its main component is keratin, which has high strength and chemical stability and is usually difficult to degrade naturally. Long-term accumulation not only wastes precious protein resources, but also causes serious pollution to the environment. At present, some researchers have tried to use animal hair to extract amino acids, but they mainly focus on single sulfuric acid hydrolysis or alkaline hydrolysis processes. Although this type of method can initially achieve amino acid extraction, the problems of low hydrolysis efficiency and incomplete reaction are prominent. At the same time, a large amount of waste acid and alkali liquids generated cannot be effectively recycled, further increasing the cost of waste treatment and the environmental burden. The existing process has not fully tapped the high-value utilization potential of hair resources, and has not formed a closed loop of resource utilization from raw materials to end products.

[0003] As a high-efficiency fertilizer, amino acid foliar fertilizer is widely used in agricultural production due to its characteristics of rapid absorption and easy use. However, the preparation of traditional foliar fertilizers mainly relies on chemical synthesis of amino acids or extraction of amino acids from plants. The former is costly and not environmentally friendly, and the latter is subject to the limited supply and seasonal restrictions of plant raw materials, resulting in single product functionality and high prices. In addition, existing foliar fertilizers are usually in liquid form, which are prone to stratification and precipitation during storage, have low utilization efficiency during transportation and field application, and are not precisely designed for crop nutritional needs. At the same time, foliar fertilizers that lack slow-release function result in low nutrient absorption rate, and the frequency and amount of fertilizer use are high, which not only increases agricultural costs, but also causes waste of resources and environmental pollution.

[0004] Existing technologies have obvious deficiencies in the resource utilization of animal hair, the functional design of amino acid foliar fertilizers, and the treatment and transformation of by-products. The single hydrolysis technology cannot achieve the efficient degradation of keratin, resulting in a low extraction rate of free amino acids. Traditional by-product treatment methods are limited to simple stacking or direct discharge of waste liquid, resulting in serious waste of resources and failure to achieve high-value utilization. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing an amino acid foliar fertilizer based on animal hair extraction, which solves the problems in the prior art of low efficiency in resource utilization of animal hair, insufficient amino acid extraction, low value-added treatment of by-products, and insufficient functionality and stability of the foliar fertilizer.

[0006] To achieve the above object, the present invention is implemented by the following technical scheme: a method for preparing amino acid foliar fertilizer based on animal hair extraction, the method comprising the following steps: Raw material pretreatment: Plasma modification of animal hair to improve keratin hydrolysis performance; Double hydrolysis process: firstly, the keratin structure in the hair is decomposed by sulfuric acid hydrolysis, and then free amino acids are generated by enzymatic hydrolysis; Resource utilization of by-products: the undissolved residues produced during the hydrolysis process are prepared as biochar or protein feed, and the amino acids and salts in the waste liquid are separated and recovered; Foliar fertilizer formula preparation: the extracted amino acid concentrate is chelated with trace elements.

[0007] Furthermore, the raw materials are first pretreated, and the collected animal hair such as pig hair, cow hair, and wool is used to improve the hydrolysis efficiency. The low-temperature plasma modification technology is used, the plasma treatment power is 100W, and the treatment time is 15 minutes to destroy the dense keratin structure on the hair surface; then a double hydrolysis process is carried out, first using 6 mol / L sulfuric acid to hydrolyze the hair with sulfuric acid, and reacting in a high-pressure reactor at 120°C and 1.2MPa for 6 hours to decompose the disulfide bonds and peptide bonds in the keratin, and the acid hydrolyzate is neutralized to pH 67 with 6 mol / L NaOH, and then filtered to remove the residue, and then keratinase and trypsin are added for enzymatic hydrolysis, the enzyme addition amount is 3% of the hair mass, and the reaction is stirred at 50°C and pH 8 for 4 hours to generate High concentration of free amino acids; at the same time, the by-products are utilized as resources. The undissolved residue is prepared into biochar through a pyrolysis process. The pyrolysis conditions are 450°C, nitrogen protection, and time for 2 hours. The residue can also be subjected to secondary enzymatic hydrolysis to prepare protein feed, and the waste liquid is separated and recovered by ultrafiltration and nanofiltration membrane technology to separate free amino acids and salts. The free amino acids are used to prepare foliar fertilizer mother liquor, and the precipitated salts such as potassium sulfate and sodium chloride can be used as basic agricultural fertilizers; in the preparation of foliar fertilizer formula, the extracted amino acids are concentrated to 30% of the total amino acid content, zinc sulfate and ferrous sulfate are added in proportion, and stable chelated trace elements are formed through citric acid-assisted chelation reaction, and the mixture is evenly mixed for subsequent treatment; finally, the product stability is optimized to prepare hormone-free foliar fertilizer.

[0008] Preferably, the animal hair includes pig hair, cow hair, wool or dried chicken hair, which is modified by low-temperature plasma treatment with a plasma power of 100 W and a treatment time of 15 minutes to improve the reactivity of keratin.

[0009] Furthermore, animal hair includes pig hair, cow hair, wool or fresh dry chicken hair, and the fresh hair is treated with low-temperature plasma. The plasma treatment is carried out in a vacuum environment, the treatment power is set to 100 W, and the treatment time is 15 minutes. The active particles of the plasma are used to effectively destroy the dense keratin structure on the surface of the hair, enhance the reaction activity of the hair to sulfuric acid hydrolysis and enzyme hydrolysis, reduce the generation of undissolved residues during the hydrolysis process, and further improve the extraction efficiency of free amino acids.

[0010] Preferably, sulfuric acid hydrolysis uses 6 mol / L sulfuric acid, and the hair and the acid solution are mixed in a mass ratio of 1:10, and the reaction is carried out in a high-pressure reactor. The reaction conditions are a temperature of 120°C, a pressure of 1.2 MPa, and a time of 6 hours; after acid hydrolysis, the hair is neutralized with a 6 mol / L NaOH solution to a pH of 6-7, and the residue is removed; enzymatic hydrolysis uses keratinase and trypsin, the enzyme addition amount is 3% of the raw material mass, the pH is adjusted to 8.0, the reaction temperature is 50°C, and the reaction time is 4 hours, wherein the reaction solution is stirred and the amino acid release rate is monitored by an online amino acid detection device, and after the reaction is completed, the solution is heated to 80°C and maintained for 15 minutes to terminate the enzyme activity.

[0011] Furthermore, the sulfuric acid hydrolysis uses 6 mol / L sulfuric acid as a hydrolysis medium, and the crushed animal hair is fully mixed with the acid solution at a mass ratio of 1:10, and the reaction is carried out in a high-pressure reactor. During the acidolysis process, the temperature in the reactor is controlled to be 120°C, the pressure is maintained at 1.2 MPa, and the reaction time is 6 hours. Through the strong oxidizing property of the acid and the synergistic effect of high temperature and high pressure, the disulfide bonds and peptide bonds in the hair keratin are destroyed, and the hair protein structure is preliminarily decomposed. After the reaction, the acidolysis solution is neutralized with a 6 mol / L NaOH solution. During the neutralization process, alkali solution is gradually added dropwise to ensure that the pH of the solution is maintained between 6 and 7 to avoid the generation of excessive by-product salts and promote the stable existence of free amino acids. The neutralized acidolysis solution is filtered to remove incompletely decomposed residues. The filtrate is used for subsequent enzymatic hydrolysis; in the enzymatic hydrolysis step, keratinase and trypsin are added to the acid hydrolyzate for synergistic action, the amount of enzyme added is 3% of the mass of the raw material, the pH of the reaction solution is adjusted to 8.0 by dripping alkali solution to maintain the optimal activity of the enzyme, the enzymatic reaction temperature is controlled at 50°C, the reaction time is 4 hours, the uniformity of the reaction solution is maintained by a stirring device, and the release rate of free amino acids is monitored in real time by an online amino acid detection device to determine the progress of the enzymatic reaction. When it is detected that the amino acid release amount reaches a stable level, the enzymatic hydrolysis is stopped and the reaction solution is heated to 80°C and maintained for 15 minutes to inactivate the enzyme activity to prevent excessive reaction in subsequent processing, while ensuring the quality and concentration of the free amino acids, and finally obtaining a solution rich in free amino acids for subsequent concentration and foliar fertilizer preparation.

[0012] Preferably, the undissolved residue is subjected to a pyrolysis process to prepare biochar, the specific steps of which include: The residue was pre-dried and carbonized at 200°C to remove most of the water and volatiles; The carbide was placed in a pyrolysis furnace at 450°C with nitrogen protection for 2 hours. The pyrolyzed biochar was treated with acid and alkali activation by soaking in 5% HCl and 5% NaOH solutions for 30 minutes each to increase the specific surface area and porosity. The biochar is used to improve the nutrient adsorption performance of the soil or as an active carrier of a slow-release fertilizer.

[0013] Furthermore, the undissolved residue separated from the sulfuric acid hydrolysis and enzyme hydrolysis processes was preliminarily treated by placing it in a heating environment at 200°C for pre-drying and carbonization. This step removes most of the moisture and volatile organic matter in the residue by low-temperature decomposition, reduces the volume of the residue and prepares for subsequent high-temperature pyrolysis. The pretreated carbide is then sent to a pyrolysis furnace for high-temperature pyrolysis treatment. The pyrolysis conditions are 450°C. Nitrogen is introduced during the pyrolysis process to ensure an oxygen-free environment, prevent the residue from burning and maintain its internal structural integrity. The pyrolysis time is 2 hours. The keratin residues and other organic components are converted into a stable carbonaceous structure through high temperature. After the pyrolysis is completed, the resulting biochar is placed in a cooling environment. Subsequently, an acid-base activation treatment was carried out. The specific method was to soak the biochar in 5% HCl solution and 5% NaOH solution for 30 minutes each, and the acid solution was used to remove inorganic impurities on the surface of the biochar and the alkali solution was used to further expand its pore structure, thereby significantly increasing the specific surface area and porosity of the biochar; after rinsing with clean water to neutrality and fully drying, the activated biochar was obtained. The biochar can be used as a functional material for improving soil, using its high specific surface area to adsorb and release soil nutrients, thereby improving soil fertility and retaining moisture, and can also be used as an active carrier for slow-release fertilizers, slowly releasing the encapsulated amino acids and other nutrients through its porous structure, effectively extending the release cycle of the fertilizer, and improving the utilization efficiency of the fertilizer and the growth effect of the crop.

[0014] Preferably, the waste liquid is processed for resource recovery through the following steps: Ultrafiltration separation: Ultrafiltration membrane (pore size 0.01μm) is used to remove high molecular weight proteins and suspended matter, and the filtration pressure is 0.5MPa; Nanofiltration concentration: Concentrate free amino acids and in the wastewater through a nanofiltration membrane system; Salt extraction: The remaining liquid is concentrated to a dry matter content of 50% by an evaporation device, and potassium sulfate and sodium chloride crystals are precipitated, of which the potassium sulfate content reaches more than 80%. The crystals are used as basic agricultural fertilizers to improve the nutrient supply of crops.

[0015] Furthermore, the waste liquid is firstly separated by an ultrafiltration membrane system. The pore size of the ultrafiltration membrane used is 0.01 μm, and the operating pressure of the ultrafiltration system is controlled at 0.5 MPa. The ultrafiltration technology is used to effectively remove high-molecular-weight proteins and suspended particles in the waste liquid, thereby ensuring the clarity of the waste liquid and providing efficient pre-filtration liquid for subsequent treatment; the ultrafiltration liquid enters the nanofiltration membrane system, and the free amino acids in the waste liquid are concentrated by nanofiltration. During the nanofiltration process, small molecular solutes are separated from inorganic salts, and the free amino acids achieve a recovery rate of more than 90% in the nanofiltration operation, and are concentrated into a high-content amino acid solution, which is convenient for further application in the preparation of foliar fertilizer mother solution; for nanofiltration, The salt solution left after filtration is treated by an evaporation concentration device, and the solution is evaporated to a dry matter content of 50%. Potassium sulfate and sodium chloride crystals are precipitated under controlled temperature and crystallization conditions, wherein the purity of potassium sulfate is controlled to be above 80%. The crystallized product is obtained by centrifugation and drying processes to obtain the final solid fertilizer; the potassium sulfate crystals and sodium chloride crystals can be used as basic agricultural fertilizers to improve the potassium nutrition supply of crops, improve crop stress resistance and photosynthesis efficiency, and at the same time, the salt products that utilize waste liquid resources help reduce the cost of waste treatment, realize high-value reuse of waste, and improve the economy and environmental benefits of the entire production process.

[0016] Preferably, the amino acid concentrate is prepared by the following process: The enzymatic hydrolyzate was concentrated to a total amino acid concentration of 30% by evaporation under reduced pressure; Adjust the amino acid ratio so that lysine accounts for 12%, glutamic acid accounts for 18%, and glycine accounts for 10%; During the concentration process, 0.05% antioxidant (such as ascorbic acid) is added to prevent amino acid oxidation and ensure solution stability.

[0017] Furthermore, the amino acid solution obtained by sulfuric acid hydrolysis and enzyme hydrolysis is subjected to reduced pressure evaporation and concentration treatment. The operating pressure of the reduced pressure evaporation is set at 0.08 MPa, and the evaporation temperature is controlled below 50°C to reduce the risk of thermal degradation of amino acids by high temperature. The evaporation process continues until the total amino acid concentration reaches 30%. Continuous stirring is used during the concentration process to ensure the uniformity of the solution and prevent oxidation caused by local overheating. After the concentration is completed, the composition ratio of the amino acids is detected, and the content of key amino acids in the solution is adjusted according to agricultural needs, specifically, the proportion of lysine is adjusted to 12%, the proportion of glutamic acid is adjusted to 18%, and the proportion of glycine is adjusted to 10%. The amino acid distribution is optimized by controlling the raw material ratio or introducing targeted modifications in the reaction stage to ensure the nutrient balance of the product and the plant absorption efficiency. In order to avoid oxidative degradation of amino acids during the concentration process, 0.05% ascorbic acid is added as an antioxidant. Ascorbic acid inhibits the occurrence of oxidation reactions in the solution through reduction, maintains the chemical stability and functional activity of amino acids, and the concentrate is filtered to remove trace precipitation and stored in a light-proof and sealed container to prevent quality degradation during subsequent storage, so as to provide high-quality mother liquor for foliar fertilizer formulation.

[0018] Preferably, trace element chelation is accomplished by the following steps: Add zinc sulfate and ferrous sulfate to the amino acid solution at 0.5% of the volume of the mother solution; The solution pH was adjusted to 6.0, and citric acid was used as an auxiliary chelating agent to enhance the stability of the chelation reaction; The solution was heated to 60° C. and stirred for 1 hour. The formation of the chelate was confirmed by infrared spectroscopy.

[0019] Furthermore, zinc sulfate and ferrous sulfate are added to the prepared amino acid solution. These trace elements exist in the form of sulfates and have high solubility and stability. The addition amount is calculated as 0.5% of the volume of the amino acid mother solution. Precipitation or uneven reaction caused by local excessive concentration is avoided by gradual addition. After adding the trace elements, the pH of the solution is adjusted to 6.0 using a precise pH adjustment device. The pH adjustment is performed by slowly dropping a diluted NaOH or HCl solution to maintain the stability and uniformity of the system. At the same time, citric acid is added to the solution as an auxiliary chelating agent. Citric acid can form a more stable chelating agent with the trace elements through its carboxyl group. A stable chelate complex is added to improve the efficiency of the chelate reaction and the storage stability of the finished product; the solution is then heated to 60°C, a mechanical stirring device is used to keep the solution in a uniform mixing state, and the chelate reaction is maintained for 1 hour. During this process, the trace elements gradually combine with amino acids to form a chelate complex. The reaction solution is detected in real time using infrared spectroscopy, with a focus on changes in characteristic peaks to confirm the formation and quality of the chelate. The adequacy of the reaction and the consistency of the product are ensured by optimizing the temperature, time and stirring rate. Finally, the chelate solution is cooled and filtered for further preparation of foliar fertilizer, providing crops with efficiently absorbed chelated trace element nutrition.

[0020] Preferably, the foliar fertilizer after chelating trace elements is directly used for fertilizer preparation after removing impurities by centrifugation.

[0021] Preferably, the stabilizer comprises polyphosphate and sodium citrate, wherein the addition ratio of polyphosphate is 0.3% and the addition ratio of sodium citrate is 0.1%; the sustained-release material comprises a starch-based composite and chitosan, and the ratio is 75:25: The amino acid solution and the sustained-release material are mixed evenly, and the concentration of the solution is controlled to be 30%; Furthermore, the stabilizer includes polyphosphate and sodium citrate, wherein polyphosphate is the main stabilizing component and its addition ratio is 0.3%. By complexing with trace elements and amino acid molecules in the solution, it can effectively prevent precipitation or crystallization during storage, thereby maintaining the uniformity of the fertilizer solution. The addition ratio of sodium citrate is 0.1%. As an auxiliary stabilizer, it can further enhance the stability of the solution by complexing metal ions and at the same time play a role in regulating the pH of the solution; the slow-release material uses starch-based complexes and chitosan in a ratio of 75:25, wherein the starch-based complex has excellent coating ability after modification, and chitosan has good film-forming and biodegradability. The combination of the two can ensure that the slow-release particles can maintain structural stability and gradually release nutrients during use. The specific steps of preparing the slow-release particles include: mixing the extracted amino acid solution with the pre-prepared slow-release material in a certain ratio, using a low-speed agitator to maintain uniformity during the mixing process, and adjusting the concentration of the amino acid solution to 30% to ensure efficient dispersion of nutrients during the coating process Preferably, the foliar fertilizer is finally prepared as a liquid, which is suitable for long-distance transportation and field application.

[0022] Furthermore, the foliar fertilizer is finally prepared into a liquid. The density uniformity of the liquid has been tested and verified. It can quickly release nutrients after application, effectively covering the nutrient absorption area of ​​crop leaves, further improving the utilization efficiency and fertilization effect of the fertilizer, and meeting the diverse needs of agricultural production for high-performance foliar fertilizers.

[0023] The present invention provides a method for preparing amino acid foliar fertilizer based on animal hair extraction, which has the following beneficial effects: 1. The present invention achieves the technical effect of "zero emission" and high-value conversion of waste by preparing biochar through a pyrolysis process of the undissolved residue or preparing protein feed through secondary enzymatic hydrolysis, and separating and recovering free amino acids and salts in the waste liquid through membrane separation and crystallization extraction technology. Compared with the technical solution in the prior art that only simply separates the hydrolyzate and ignores the resource utilization of by-products, it solves the environmental pollution problem caused by residue accumulation and waste liquid discharge. The biochar made from the treated undissolved residue not only has a high specific surface area and porosity, but can also be used to improve soil and as a slow-release fertilizer carrier.

[0024] 2. The present invention adopts a pretreatment technical solution that combines low-temperature plasma surface modification of animal hair, which effectively destroys the dense structure of keratin on the hair surface and significantly improves the reaction efficiency and product extraction rate of the subsequent hydrolysis process. Compared with the technical solution in the prior art that simply relies on sulfuric acid hydrolysis or mechanical crushing, it solves the problems of low sulfuric acid hydrolysis efficiency, insufficient enzymatic hydrolysis products and high undissolved residues caused by the integrity of the hair surface structure.

[0025] 3. The present invention achieves the technical effect of preparing foliar fertilizer products with diverse functionality, high stability and long-term slow-release performance by adopting the technical solution of chelating trace elements and compounding foliar fertilizers, and combining the stabilizer system of polyphosphate and sodium citrate and the technical route of preparing slow-release particles with starch-based composites and chitosan coating materials. Compared with the single-function liquid foliar fertilizer technical solution in the prior art, the present invention solves the shortcomings of the existing foliar fertilizers that are easy to stratify and precipitate during storage and have low absorption and utilization rate after application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Please refer to the attached Figure 1 : Example 1: Example of innovative ingredients with values ​​within the range Raw material pretreatment: Take 100g of pig hair and treat it with 100W low-temperature plasma for 15 minutes.

[0029] Sulfuric acid hydrolysis: Hair was mixed with 6 mol / L hydrochloric acid at a mass ratio of 1:10 and reacted at 120°C and 1.2 MPa for 6 hours.

[0030] Enzymatic hydrolysis: neutralize the acid hydrolyzate to pH 6.5, add keratinase and trypsin (enzyme addition amount is 3%), adjust the reaction solution to pH 8.0, stir the reaction at 50°C for 4 hours, and monitor the release of amino acids.

[0031] Utilization of by-products: The undissolved residue is pyrolyzed to 450°C to prepare biochar, and the waste liquid is separated into free amino acids by ultrafiltration and nanofiltration.

[0032] Foliar fertilizer preparation: Add 0.5% zinc sulfate and 0.5% ferrous sulfate, use citric acid chelation, adjust the pH to 6.0, heat to 60°C, and stir for 1 hour to prepare foliar fertilizer.

[0033] Example 2: Example with innovative ingredients below the range value Raw material pretreatment: 100 g pig hair, low-temperature plasma power set to 50 W, treatment time 10 minutes.

[0034] Sulfuric acid hydrolysis: The concentration of hydrochloric acid was reduced to 4 mol / L, the mass ratio of hair to acid solution was 1:12, and the reaction was carried out at 120°C and 1.0 MPa for 4 hours.

[0035] Enzyme hydrolysis: The enzyme addition amount was reduced to 2% and the reaction time was 3 hours.

[0036] Utilization of by-products: The residue is simply dried without thermal decomposition, and the waste liquid is only separated by nanofiltration.

[0037] Foliar fertilizer preparation: Add 0.3% zinc sulfate as trace elements and reduce the amount of citric acid by half.

[0038] Example 3: Example with innovative ingredients above the range value Raw material pretreatment: 100g pig hair, low-temperature plasma power increased to 150W, treatment for 20 minutes.

[0039] Sulfuric acid hydrolysis: The concentration of hydrochloric acid was increased to 8 mol / L, the mass ratio of hair to acid solution was 1:8, and the reaction was carried out at 130°C and 1.5 MPa for 8 hours.

[0040] Enzyme hydrolysis: The enzyme addition amount was increased to 5%, and the reaction time was 5 hours.

[0041] Utilization of by-products: The residue is used to prepare biochar and then treated with acid and alkali activation, and the waste liquid is separated by ultrafiltration and then nanofiltration.

[0042] Foliar fertilizer preparation: Add 0.7% zinc sulfate as a trace element and increase the concentration of the auxiliary chelating agent citric acid to 0.2%.

[0043] Example 4: Example of preparing protein feed Treatment of undissolved residue: After enzymatic hydrolysis, the undissolved residue was subjected to secondary enzymatic hydrolysis (trypsin, 2% addition) at 50°C for 2 hours.

[0044] Protein extraction: Add 0.05% antioxidant, concentrate under reduced pressure to a protein concentration of 50%, and dry to prepare protein feed.

[0045] Effect: The protein content of the residue used as feed is increased to 60%.

[0046] Example 5: Example of slow-release fertilizer Foliar fertilizer concentrate: The amino acid concentration is adjusted to 30%, and a starch-based complex and chitosan (75:25) are added to prepare a slow-release fertilizer.

[0047] Granulation: Made into granular fertilizer and tested for slow-release performance.

[0048] Comparative experiment Comparative Example 1: Lack of resource utilization of undissolved residue Existing technical solution: the enzymatic residue is not treated and is directly discarded.

[0049] Result: A large amount of residue accumulates, causing environmental pollution.

[0050] Comparative Example 2: Lack of low temperature plasma treatment Prior art solution: direct sulfuric acid hydrolysis of hair without surface modification.

[0051] Results: The efficiency of sulfuric acid hydrolysis decreased by 15%, and the proportion of undissolved residue increased by 30%.

[0052] Comparative Example 3: No trace element chelation Existing technical solution: direct foliar fertilizer preparation without adding chelating agent.

[0053] Results: The stability of trace elements in foliar fertilizer was reduced, and the absorption rate after application was only 65%.

[0054] Experimental data table Table 1: Comparison between resource utilization and “zero emission” Technical Solution Undissolved residue treatment rate Waste liquid recovery rate Environmental pollution index The present invention 95% 90% 5% Prior art 50% 60% 30% Table 2: Comparison of hydrolysis efficiency and product extraction rate Technical Solution Sulfuric acid hydrolysis efficiency Enzyme hydrolysis efficiency Amino acid extraction rate The present invention 85% 90% 88% Prior art 70% 60% 65% Table 3: Comparison of functional diversity and stability Technical Solution Functional indicators Storage stability Sustained release performance The present invention Versatile High stability excellent Prior art Single function Low stability ordinary Summarize Through examples and comparative experiments, it is demonstrated that the present invention has significant advantages in "zero emission" of waste, high-value conversion, improved reaction efficiency, and functionality and stability of foliar fertilizer, providing a technical solution for sustainable development of agricultural production.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing amino acid foliar fertilizer based on animal hair extraction, characterized in that: The method comprises the following steps: Raw material pretreatment: Plasma modification of animal hair to improve keratin hydrolysis performance; Double hydrolysis process: firstly, the keratin structure in the hair is decomposed by sulfuric acid hydrolysis, and then free amino acids are generated by enzymatic hydrolysis; Resource utilization of by-products: the undissolved residues produced during the hydrolysis process are prepared as biochar or protein feed, and the amino acids and salts in the waste liquid are separated and recovered; Foliar fertilizer formula preparation: the extracted amino acid concentrate is chelated with trace elements.

2. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: The animal hair includes pig hair, cow hair, wool or dried chicken hair, which is modified by low-temperature plasma treatment with a plasma power of 100 W and a treatment time of 15 minutes to improve the reactivity of keratin.

3. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: The sulfuric acid hydrolysis uses 6 mol / L sulfuric acid, and the hair and the acid solution are mixed in a mass ratio of 1:10 in a high-pressure reactor. The reaction conditions are a temperature of 120°C, a pressure of 1.2 MPa, and a time of 6 hours. After the acid hydrolysis, the hair is neutralized with a 6 mol / L NaOH solution to a pH of 6-7, and the residue is removed. The enzymatic hydrolysis uses keratinase and trypsin, and the enzyme addition amount is 3% of the raw material mass. The pH is adjusted to 8.0, the reaction temperature is 50°C, and the reaction time is 4 hours. The reaction solution is stirred and the amino acid release rate is monitored by an online amino acid detection device. After the reaction is completed, the solution is heated to 80°C and maintained for 15 minutes to terminate the enzyme activity.

4. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: The undissolved residue is pyrolyzed to produce biochar, the specific steps of which include: The residue was pre-dried and carbonized at 200°C to remove most of the water and volatiles; The carbide was placed in a pyrolysis furnace at 450°C with nitrogen protection for 2 hours. The pyrolyzed biochar was treated with acid and alkali activation by soaking in 5% HCl and 5% NaOH solutions for 30 minutes each to increase the specific surface area and porosity. The biochar is used to improve the nutrient adsorption performance of the soil or as an active carrier of a slow-release fertilizer.

5. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: Wastewater is recycled through the following steps: Ultrafiltration separation: Ultrafiltration membrane (pore size 0.01μm) is used to remove high molecular weight proteins and suspended matter, and the filtration pressure is 0.5MPa; Nanofiltration concentration: Concentrate free amino acids and in the wastewater through a nanofiltration membrane system; Salt extraction: The remaining liquid is concentrated to a dry matter content of 50% by an evaporation device, and potassium sulfate and sodium chloride crystals are precipitated, of which the potassium sulfate content reaches more than 80%. The crystals are used as basic agricultural fertilizers to improve the nutrient supply of crops.

6. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: The amino acid concentrate is prepared by the following process: The enzymatic hydrolyzate was concentrated to a total amino acid concentration of 30% by evaporation under reduced pressure; Adjust the amino acid ratio so that lysine accounts for 12%, glutamic acid accounts for 18%, and glycine accounts for 10%; During the concentration process, 0.05% antioxidant (such as ascorbic acid) is added to prevent amino acid oxidation and ensure solution stability.

7. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: Trace element chelation is accomplished through the following steps: Add zinc sulfate and ferrous sulfate to the amino acid solution at 0.5% of the volume of the mother solution; The solution pH was adjusted to 6.0, and citric acid was used as an auxiliary chelating agent to enhance the stability of the chelation reaction; The solution was heated to 60° C. and stirred for 1 hour. The formation of the chelate was confirmed by infrared spectroscopy.

8. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: The foliar fertilizer after chelating the trace elements is directly used for fertilizer preparation after the impurities are removed by centrifugation.

9. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: The stabilizer includes polyphosphate and sodium citrate, wherein the addition ratio of polyphosphate is 0.3% and the addition ratio of sodium citrate is 0.1%; the sustained-release material is a starch-based composite and chitosan, and the ratio is 75:25: The amino acid solution and the sustained-release material were mixed evenly, and the concentration of the solution was controlled to be 30%.

10. The method for preparing amino acid foliar fertilizer based on animal hair extraction according to claim 1, characterized in that: The foliar fertilizer is finally prepared into a liquid, which is suitable for long-distance transportation and field spreading.

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